Embryos need a lot of energy to grow, but as women get older, the "power plants" of the cells (called mitochondria) don't work as well. This makes it harder for embryos to develop normally. One possible way to help is with a gentle light treatment called photobiomodulation (PBM). This uses a special type of red light that boosts energy production in cells and helps them stay healthy. This study will test whether adding this light treatment during in vitro fertilization (IVF) can improve embryo growth and pregnancy chances.

Embryo development is highly energy-dependent, and impaired mitochondrial function is a well-established hallmark of reproductive aging. As women age, reactive oxygen species (ROS) accumulate and cause mitochondrial DNA (mtDNA) damage, leading to reduced oxidative phosphorylation, ATP (Adenosine 5'-triphosphate) depletion, and developmental arrest of embryos. Enhancing mitochondrial function represents a promising strategy to improve embryo quality, particularly in women of advanced maternal age.

Photobiomodulation (PBM), also known as low-level light therapy (LLLT), involves the application of low-intensity red or near-infrared (NIR) light to modulate mitochondrial activity. NIR light specifically activates cytochrome c oxidase, leading to increased ATP production, reduced oxidative stress, and improved cellular resilience. Numerous preclinical studies, including isolated mitochondria, cell cultures, and in vivo animal models, have confirmed the safety and efficacy of NIR light in restoring mitochondrial function without inducing DNA damage or chromosomal abnormalities.

The investigators previously conducted IRB-approved laboratory studies using mouse and donated human embryos, demonstrating that brief exposure to PBM improved blastocyst formation without adversely affecting chromosomal status.

The current study builds upon this foundational work to evaluate the clinical impact of PBM during embryo culture in IVF. In a randomized, blinded, sibling-embryo design, the investigators will test whether PBM improves blastocyst formation, embryo quality, and pregnancy outcomes in participants undergoing IVF or ICSI (Intracytoplasmic sperm injection) with PGT-A (preimplantation genetic testing for aneuploidy) using their autologous oocytes.

Inclusion Criteria:

• Female age between 18-48 years at time of IVF/ICSI cycle
• Undergoing blastocyst culture and PGT-A
• Using own oocytes
• Have at least two fertilized eggs available for randomization
• Consenting to embryo-level randomization
• Plan to transfer euploid embryo within 6 months

Exclusion Criteria:

• Use of donor eggs
• Known uterine or genetic anomalies
• Refusal of randomization or request for non-standard handling

All embryos will be coded and tracked with blinded identifiers. Embryologists selecting embryos for transfer will be blinded to treatment group. Selection will follow routine morphological and PGT-A criteria.